Apparatus for pressure forming toothed elements



July 10, 1962 w. B. MCCARDELL APPARATUS FORPRESSURE FORMING TOOTHED ELEMENTS Filed May 14, 1959 3 Sheets-Sheet 1 Nw 1 4 Ww w Nw FJ www Q ww ww a u Ww e m MBNA M p M Y QL w a u H nw.- I

July 10, 1962 w. B. MocARDl-:LL

APPARATUS FOR PRESSURE FORMING TOOTHED ELEMENTS 5 Sheets-Sheet 2 Filed May 14, 1959 l/ Clan/wier July 10, 1962 W. B. MCCARDELL 3,043,169

APPARATUS FOR PRESSURE FORMING TOOTHED ELEMENTS Filed May 14, 1959 3 Sheets-Sheet 3 United States Patent 3,043,169 APPARATUS FOR PRESSURE FORME TOOTmD EIEIVEN'IS Willard B. McCardell, Royal Oak, Mich., assigner to Michigan Tool Company, Detroit, Mich., a corporation of Delaware Filed May 14, 1959, Ser. No. 813,234 Claims. (Cl. Sil-16) This invention relates to apparatus for pressure forming teeth on toothed elements such as spline shafts, Worms, gears, and the like, and more particularly, to improved tools for pressure lforming external teeth on such toothed elements.

An object of the invention is to overcome disadvantages in prior tools of the indicated character and to provide improved tooling for pressure forming teeth on toothed elements which will reduce the cost of-manufacturing the toothed elements, increase the speed of production, and improve the quality thereof.

Another object of the invention is to provide improved apparatus for pressure forming toothed elements which is simple in construction, durable, eicient and reliable in operation, and which may be manufactured with a minimum of labor and expense.

The above as well as other objects and advantages of the present invention will become apparent from the following description, the appended claims, and the accompanying drawings, wherein:

FIGURE l is a schematic and simplified illustration, in side elevation and with parts removed, of apparatus embodying the'present invention;

FIGURE 2 is a sectional view of the structure illustrated in FIGURE 1, taken on the line 2-2 thereof;

FIGURE 3 is a simplified and schematic circuit diagram of the mechanism for driving thevapparatus illustrated in FIGURE l, with the control valve enlarged and the direction of one of the tool moving pressure cylinders reversed for purposes of illustration;

FIGURE 4 is a fragmentary view of a typical involute spline that can be formed by the tool of the present invention; l

FIGURE 5 is an enlarged side-elevational view of the tooland tool holder illustrated 'm FIGURE 1;-

FIGURE 6 is a top plan view of the apparatus illustrated in FIGURE 5;

FIGURE 7 is an enlarged view of one of the tools illustrated inFIGURE l;

FIGURE 8 is an enlarged sectional view in a radial plane of one of the teeth of the tool illustrated in FIG- URE 7; and

FIGURE 9 is an end view of another embodiment of the invention showing the same applied to `a workpiece.

Referring to the drawings, preferred embodiments of the invention are illustrated. lIn FIGURES 1 and 2 a workpiece W is shown in position between the upper and lower tools 1 and 3 embodying thepresent inventiqgm,v the ,tools 1 and 3 being shown at the beginning of thefoperation which will pressure form involutel teeth 4 on theLk periphery of the workpiece W. The workpiece WV isjsupported by means which permit it to rotate freely on a iixed axis when urged todo so by the tools 1 and 3. At

.the Sametime, the workpiece is fed axially between the toolsfor any desired distance to form teeth 4 of the desired length on the workpiece. Thus, reciprocation of the cylindrical tools 1 and3 is combined with an axial feed of the workpiece W so as to roll involute teeth of any reasonable length on the workpiece.l The tools 1 and 3 are reciprocated relative to the workpiece W in a relatively short but fast travel, and as the reciprocating tools follow a straight path, the workpiece W isl axially fed until the desired tooth'length is obtained. By way of example, with ICC i tools approximately nine inches long, the axial feed rate of the workpiece may be in the order of from JAG to 1/s inch per tool stroke depending on the workpiece diameter, pitch, and desired nish. To illustrate such means, there is known in FIGURE 2 a center -pin 5 which is carried by an axially movable member 7 which may be mounted for reciprocation in the apparatus or machine 8 which carries the tools 1 and 3. The workpiece supporting means is also shown as including a center pin 9 carried by the piston rod 10 of a conventional piston and cylinder until that is also supported by the apparatus on which the tools 1 and 3 are mounted. Means may be provided for adjusting the piston and cylinder unit so as to provide adjustments whereby varying lengths of workpieces W may be handled by the machine.

The Aupper and lower tools 1 and 3 are identical and include a body portion 11 having teeth 12 extending circumferentially around the periphery thereof that engage the surface of the workpiece W. The tools 1 and 3 are movable axially by suitable means and are illustrated herein as being slidable on ways 15 and 17 the tools 1 and 3 being carried by tool holders, generally designated 18, which will be described hereinafter in greater detail. The ways 15 and 17 are shown as being formed in the head 19 and bed 21, respectively, of the machine 8 which carries the tools.

Means are provided for simultaneously moving the tools 1 and 3 in opposite directions. This means is illustrated inFIGURES l and 3 as comprising a pair of identical pressure cylinders 213 and 24 having pressure ports 25 and 26 at one end and pressure ports 27 and 28'at the opposite end. Pistons 29 and 30 are mounted for reciprocation in the cylinders, the pistons having rods 31 and 32. The rod 31 is ixedto the trailing end of a tool slide 33 mounted on the Ways 15 `While the rod 32 is fixed to the trailing end of a tool slide 34 mounted on the ways 17. Suitable valving is provided which may be used to control Y the fluid pressure in the cylinders 23 and 24 so as to actuate and synchronize the movement of the pistons whereby the tools 1 and '3 move at the same instant and at the same velocities in opposite directions. By way of illustration, in FIGURE 3 the cylinder ports 25 and 26 are shown as being joined together by a T connector and are connected by the line 35 to the port 36 while the cylinder ports 27 and 2S are joined together by a T con- ,nector and connected by the line 37 to the port 39. A

three land spool valve 41 is provided in a Valve casing 43, the spool valve 41 being shiftable to the right so as to connect the ports 25 and 26 to pressure from a pump 45 andy to connect ports 27 and 28 to tank. By shifting the spool valve 41 to the left, the reverse condition is obtained whereby ports 25 and 26 are connected to tank and the ports 27 and 28 are connected to pressure.

. In the operation of the apparatus as above described, with the tool 1 and 3 in the positions shown in FIGURES l and 2, the workpiece W is mounted on :the centers 5 and 9 which permit the workpiece to be rotated by the tools 1 and 3. The valve 41 is moved to the left so as to connect the ports 27 and 28 to pressure and to connect the ports 25 and 26 to tank so that the tool 1 moves to the left and the tool 3 rnoves to the right, as viewed in FIGURE l. The spacing between the tools 1 and 3, measured in a vertical plane which includes the longitudinal ax of both of the tools 1 and 3 is such that the distance between the tips of the teeth of the tools 1 and 3 is less lthan the original diameter of the workpiece W. Thus, the shape or configuration of the teeth 12 of each tool 1 and 3 is impressed or conjugated on the periphery of the workpiece W. At the same time that the tools 1 and 3 are reciprocated past the workpiece, the workpiece is preferably continually axially fed so as to increase the length of the teeth 4 being formed on the workpiece. The tools 1 and 3 are reciprocated back and forth past the workpiece while the workpiece iscontinually fed axially until the desired spline or gear tooth length is obtained, the teeth on the tools generating the teeth formed on the workpiece. After the desired length of the teeth on the workpiece is obtained, the workpiece is removed from between the tools by withdrawing the workpiece tothe right, as Viewed in FIGURE 2, after which a new workpiece can then be inserted in the apparatus and the operation repeated.

' In rolling involute teeth `of the desired shape, as for example spline teeth having a 30 or a 45 pressure angle, into the workpiece, the workpiece material will llow adjacent the surface in radial and tangential directions so as to form grooves of less than the original diameter of the workpiece and teeth of greater diameter than the original "diameter ofthe workpiece. This -ow of material is taken into account in selecting the diameter of that portion ofthe workpiece which is to be subjected to the action of the tools 1 vvand 3. l. j

Referring to FIGURE 4, a common .involute toothrshape figuration. As wear occursfthe tools 1 and 3Y may be is illustrated which may be rolled by means'of the tools ern-V bodying the present invention. In FIGURE 4 a portion of a cross section of a workpiece W is nished form'is illustrated1 the workpiece having involute teeth or splines 4. Since no metal is lremoved in the rolling operation,

the diameter ofthe workpiece W prior'to rolling cannot be either the nal outside diameter or the root diameter.

indexed in the holders 18 to bring an unworn portion of the forming teeth 12 into use. Indexing thus per-mits several settings for each tool before the tools become worn and unserviceable. As shown in FIGURES 2, 5 and 6, each tool holder 1S is comprised of a base 50 to which are xcd end members 52 and 5'4 and a back member 56, the base being secured to the -associated slide member 33 or 34 by bolts 58. As shown in FIGURE 2, theYY base SlIis provided With'a taperedrramppo'rton 60 upon which the periphery of the tool rests while the back member 56 carries a generally wedge-shaped retainer 62 which also engages the periphery of the tool and serves to prevent vertical movement of the tool, In `order to permit workpieces to be withdrawn' from between the tools l and 3 after Ythe tooth-forming operation, a plurality of spaced, resilient bumper members 64 are provided which are carried by posts 66 secured to the'base 5G, suitable spacers 68 being provided to'finsure that the bumpers are carried at the desired height. With the above described construction, when axial feeding movement is imparted to the workpiece W, the tools 1 and 3 are forced transversely of each base 50 so 'that the tools 1 and 3 are wedged between theV taperedA surface 70k of the ramp 60 and the wedge or tapering surface 72 of the retainers 62 to hold the tools securely in the proper position. In order to provide for indexing movement of the tools lgand 3 after The rolling diameter D1 of the workpiece W is selected so that the area 57 of displaced tooth material inside the D1 periphery is equal to the area 5.9 of tooth material on a greater diameter than D1. The diameter D1, or substantially this diameter, is taken as the tool pitch diameter P.D. and denes the pitch cylinder P.C. for the `cylindrical tools 1 Iand 3, the pitch cylinder being tangent to the rolling diameter D1 of the workpiece. The pressure angle of the teeth 12 of the tools at the diameter D1 and the pressure angle or angle of obliquityof the, teeth 4 of the workpiece at the diameter D1 isv the angle whoseV cosine is D/D1 multiplied by the cosine of the pressure angle at kthe pitch diameter of the teeth 4 where D is the pitch diameter of the workpiece W.V The base pitch ofthe tools and `of the workpiece are identical. With such la consruction, lthe circular pitch of the lteeth 12 on the tool, as measured axially on the pitch cylinder thereof, parallel to the longitudinal axis ofthe tool correspondswith the Ycircular pit-ch of the teeth 4 on the workpiece, as measured on a circle having the diameter D1 of the workpiece. VThe whole depth'of all of the Ateeth 1'2 on each tool 1 and 3Y which engage the workpiece W is the sameas that of the workpiece, i.e., Yall. ofthe toolteethlZ arerfully conjugate to the teeth 4. on 'the workpiece.

v'the present invention, that the teeth 12'of the tools will Since,v in transverse crossl section, the teeth 12 on Ythe is axially fed between the tools while .the tools areY re-V ciprocating, the maximum'penetration being effected ina .plane which is perpendicular to the longitudinal axis of the workpiece and which includes the longitudinal axes of both of the tools. As the workpiece continues to move past the center line of action between the tools, the pressure exerted on the workpiece by the Ytools is gradually decreased as the.

fully formed portion ofthe workpiccermoves free of the tools. f* f As shown in FIGURE 7, in this embodiment of lthe in-V vention, all of the teeth 12 on the tools are perpendicular to the longitudinal axes of the tools. Thus, the pitch cylp inder of the tool teeth V1.2 defines an innite number of pitch Y lines Yparallel to thelongitudinal axis of each tool, and in any radialplane which includes the axis of the tool, all

of the teeth 12 on the toolV are fullsized .and fully conjugate to the lteeth on the workpiece.

The tools 1 and 3 are preferably precision made of high K alloy `steel and -may be readily ground to the desired con- Ythey become worn, suitable pins 74 are xed -to the base 50, the free ends of the pins 74 Ibeing taperedjas at 76 so as to fit in angularly spaced, radial slots 78 provided in the end:portions of the tools 1 and 3. With such a construction the toolsvare permitted to rock about the tapered ends 76 of the pins 74 thereby permitting the, tools land 3 to f spread aparta suicient distance to permit the workpiece to be withdrawn from between the tools after the toothforming operation by compressing the resilient bumpers 64, .the bumpers serving to rock the tool back against the tapered surfaces 70 and 72 to the correct tooth-forming position after the workpiecehas been withdrawn.

It will be noted that in settingV up the tools embodying :be in a direct'vertical lline with'one another when vform- 111g an even number of teethbut/l/z pitch yapart when forming an odd number of teeth. In order to permit correct adjustment of the tools, an adjustable 'abutmenty stop 80 is provided in the end member 54 of each tool holder, the adjustable abutment 'stop 80 being in the form` of a threaded memberwhich maybe adjusted axi- -ally of the associated' tool,"suitable shim means being provided at the opposite end of the tool-so that each tool may be properly s'et up and Valigned with its mating tool. As shown in FIGURE 9, when it is desired to form vteeth on a workpiece W havinga'shoulder 90, each ltool T can be longitudinally Vnotched as `at 92 so that full-depth teeth 4' can be formed in the workpiece W up to a point closely adjacent the fshouldere9l). It will Abe appreciated thatV in this form' of theinvention, the

workpiece W is fed axially from the left toward the right as viewed in FIGURE 9. r

' While preferred embodimentsvof the invention lhave v been shown anddescribed, it will be understood that various changes `and modifications may be made without Y departing from the spirit of theY invention.

What is claimed is: f 7

1. In combination with a cylindricaltool having teeth extending around the periphery thereof, a holder for said tool, Said holder comprising a base having an upwardlytapering surfacefadjacent one'edge thereof, means carried by said base providing la wedge-shapedretainer disposed in spaced opposed relationshipwith respect to said tapered surface whereby said toolv may be wedged therebetweenjand Yresilient means carried by Ysaid base and adapted to bias said tool toward said retainer and said tapered surface.

2. In combination with a cylindrical tool having teeth Y extending around the periphery thereof, a holder for said tool, said holder `comprising -a base having an upwardly tapering surface adjacent one edge thereof, means carried by said base providing a wedge-shaped retainer disposed in spaced opposed relationship with respect to said tapered surface whereby said tool -may be wedged therebetween, resilient means carried by said lbase and adapted to bias said tool toward said retainer 4and said -tapered surface, and means carried by said base and cooperating with said tool whereby `said tool may be indexed through a predetermined 'angular increment.

3. In combination with a tool for pressure forming teeth on the periphery of a cylindrical workpiece, said tool having a body portion substantially cylindrical in cross section and being provided with teeth thereon the danks of which extend transversely of the axis of revolution of said body portion, each of said teeth in a radial plane including the axis of revolution of said body portion being conjugate to the teeth to be formed on the workpiece, each of said teeth having a pitch cylinder corresponding with the diameter of a circle which encompasses -a cross-sectional area of the interdental space between the teeth of the workpiece equal to the crosssectional area of the portions of the teeth of the workpiece outside the circle, means for supporting a said workpeice or rotation about the longitudinal Iaxis thereof, means for feeding the workpiece in a direction sub- 6 of which extend circumferentially of said tools, each of said teeth in transverse cross section being conjugate to the teeth to be formed on the workpiece and having a pitch cylinder concentric with the longitudinal axis of the body portion ofthe tool, the cross-sectional configuration of each of said teeth being substantially constant throughout the length thereof, the circular pitch of said teeth measured on 4said pitch cylinder corresponding with the circular pitch of the teeth on the workpiece measured on a circle having a diameter D1, where D1 is the diameter of a circle which encompasses a crosssectional area of the interdental space between the teeth of the workpiece equal to the cross-sectional area of the portions of the teeth of the workpiece `outside the circle, the pressure angle of each of said teeth measured at said pitch cylinder being the angle whose cosine is D/D1 multiplied by the cosine of the pressure angle at the pitch diameter D of the teeth of the workpiece, means for supporting a said workpiece for rotation about the longitudinal axis thereof, means for feeding the workpiece in a direction :substantially parallel to the longitudinal axis thereof, and means for simultaneously reciprocating said stantially parallel to the longitudinal axis thereof, and

means for reciprocating said tool in a direction transverse to the longitudinal axis of the workpiece.

4. In combination with a pair of tools for pressure forming teeth on the periphery of a cylindrical workpiece, each of lsaid ytools being provided with a substantially cylindrical body portion having teeth thereon the anks tools in opposite directions transverse to the longitudinal axis of the workpiece.

5. The combination as set forth in claim 1 wherein the body portion of each of said tools denes a longitudinal notch extending for'substantially Ithe entire length thereof. Y

References Cited in the le of this patent UNITED STATES PATENTS 2,715,846 Grob et al. Aug. 23, 1955 2,906,147 Pelphrey Sept. 29, 1959 2,995,964 Drader Aug. 15, 1961 

